package com.microservice.skeleton.upms.constraints;

import org.springframework.core.MethodParameter;
import org.springframework.util.ClassUtils;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.util.*;

/**
 * @author: lijin
 * @date: 2018年11月07日
 */
public class MethodParameterValidatorConstraintResolver extends ValidatorConstraintResolver
        implements MethodParameterConstraintResolver {

    static Class<Annotation> CONSTRAINT_CLASS;

    static {
        try {
            CONSTRAINT_CLASS = (Class<Annotation>) ClassUtils.forName("javax.validation.Constraint",
                    MethodParameterValidatorConstraintResolver.class.getClassLoader());
        } catch (ClassNotFoundException e) {
        }
    }

    @Override
    public List<Constraint> resolveForParameter(MethodParameter param) {
        if (CONSTRAINT_CLASS == null) {
            return Collections.emptyList();
        }

        List<Constraint> constraints = new ArrayList<>();
        for (Annotation annot : param.getParameterAnnotations()) {
            Class<? extends Annotation> type = annot.annotationType();
            if (type.getAnnotation(CONSTRAINT_CLASS) != null) {
                Constraint constraint = createConstraint(annot, type);
                constraints.add(constraint);
            }
        }
        return constraints;
    }

    private Constraint createConstraint(Annotation annot, Class<? extends Annotation> type) {
        Map<String, Object> configuration = new HashMap();
        for (Method method : type.getDeclaredMethods()) {
            String methodName = method.getName();
            Object value = getAnnotValue(annot, method);
            configuration.put(methodName, value);
        }
        return new Constraint(type.getName(), configuration);
    }

    private Object getAnnotValue(Annotation annot, Method method) {
        try {
            return method.invoke(annot);
        } catch (Exception e) {
            // do not fail on error, just return null as the value of the field
            return null;
        }
    }
}
